1. Field of the Invention
The present invention relates to a method for manufacturing a microstructure.
2. Description of the Related Art
A microstructure having a periodic structure is used in several devices as a grating. A microstructure made of gold which absorbs X-rays is used in a nondestructive inspection for industrial use or an X-ray examination for medical use. The nondestructive inspection or the X-ray examination utilizes the X-ray absorption contrast method to obtain an image of an object or a living body. However, it is difficult to obtain an image of a soft material or a soft tissue using these techniques because the soft material or the soft tissue absorbs only a little X-ray.
The phase contrast method, which utilizes a phase difference of X-rays, has been studied at synchrotron radiation facilities since the 1990s. The phase contrast method using an X-ray tube instead of the synchrotron (e.g. propagation-based method, Talbot interferometer method) has also been studied.
The X-ray Talbot interferometer generally uses a microstructure as an absorption grating. It is preferable that the absorption grating is made by plating a periodic structure with metal (e.g. gold). But, as a pitch of the periodic structure becomes narrower and an aspect ratio of the periodic structure becomes higher, sticking of the periodic structure occurs in more places. The aspect ratio is the ratio (h/w) of the height (depth) h to width w of the periodic structure.
When the periodic structure having many sticking places is filled with the plated metal, the absorption grating may have shifts of the pitch. So, it is difficult to obtain a desirable phase image when the X-ray Talbot interferometer uses the absorption grating having many shifts of the pitch.